The presence of biofilms in drinking water distribution systems (DWDS) is
a global concern. Those are responsible for aesthetic problems in
drinking water (DW) such as taste, odor and color, and can also be
responsible for public health problems when pathogens are biofilm
colonizers. Therefore, it is of utmost importance to use effective control
strategies. The aim of this work was to understand the effects of the
combination of chemical (sodium hypochlorite NaOCl) and mechanical
(pipe flushing) treatments on the removal of single and dual species
biofilms of two bacteria isolated from drinking water, Acinectobacter
calcoaceticus and Stenotrophomonas maltophilia. Those are common
strategies used in DWDS. A rotating cylinder reactor was used for the first
time as DWDS model for biofilm formation and control. The combination
of chemical and mechanical treatments was not able to completely
remove biofilms from polyvinyl chloride (PVC) surface. Chemical
treatment did not improve the flushing efficiency of A. calcoaceticus
biofilms and increased the recalcitrance of S. maltophilia biofilms to
mechanical treatment, even when high shear stress was applied.
Nevertheless, NaOCl improved the mechanical removal of dual species
biofilm. The dual species biofilm remaining after treatment with NaOCl at
0.5 mg.l-1 was 78%, while after being treated with the NaOCl at the
minimum inhibitory concentration 12% of biofilm remained on PVC
surface. The overall results demonstrate that chemical and mechanical
treatments commonly used in DWDS are not effective in biofilm control.
The colonizer strain strongly influences the biofilm phenotype and its
susceptibility to control strategies
